1. Field of the Invention
The present invention relates to gamma ray imaging, and more specifically, it relates to improving the gamma ray imaging efficiency and accuracy of semiconductor detectors.
2. Description of Related Art
Most gamma-ray imaging systems use position sensitive scintillators. A scintillator is a device or substance that absorbs high energy (ionizing) electromagnetic or charged particle radiation then, in response, fluoresces photons at a characteristic Stokes-shifted (longer) wavelength, releasing the previously absorbed energy. Such scintillators have good efficiency, but they lack good energy resolution, and their position resolution decreases significantly with increasing the energy of the radiation. Semiconductor detectors have the capability to provide good efficiency and position resolution, but also good energy resolution and granularity. All these features are of interest for collimator based imagers, but especially for Compton imagers. In fact the introduction of position sensitive semiconductor detectors helped revitalize the Compton scatter camera concept in the last few years. Several Compton camera devices based on CdZnTe, high purity Germanium and Silicon detectors are under development targeting applications in astrophysics, bio-medical research and homeland security. Some of these systems provide images having good resolution, but most have very low efficiency. The reason for the low efficiency is that only a fraction of the total detected photons are found suitable for Compton imaging. To obtain reasonable resolution, the average distance between the interactions must be large as compared with the position uncertainty of individual interactions, so that only events with widely separated and clean interactions can be used for imaging. Improved efficiency must be demonstrated for a Compton scatter camera to become a competitive gamma-ray imaging method.